I am newbie my site is just few month age and my alexa is 1.6 million my site is advertising and i want to make a link dev to get PR. I read some thread mention about link building using dofollow blog comment. But All thread said that you don't make a spam comment. What is that mean ?. If i comment on dofollow blog such as DP and comment some thread cause i want to comment not to make a link is it spam ?. If my comment is useful although i make a few comment in same Dofollow blog is it still spam ?. I really need answer.